This is really cool, and could enable live instrumentation for server health monitoring.
Esteban A. Maringolo 2014-06-16 12:29 GMT-03:00 Sven Van Caekenberghe <[email protected]>: > Hi, > > Here is a concrete example of how cool object logging can be. In the current > development version, Zinc HTTP Components announces a number of ZnLogEvent > objects while either ZnClient or ZnServer operates. One of those is > ZnServerTransactionEvent, which signals the completion of a single HTTP > transaction (request/response pair) by the server. By subscribing to this > specific event through Zinc's Announcer, we can simply count the number of > transactions. If we report and reset this counter every second, we get a > rudimentary live updating requests per second monitor, in about ten lines of > code in a workspace ! > > Here is the setup: > > | transactionCount transactionsPerSecond | > transactionCount := 0. > transactionsPerSecond := 0 asValueHolder inspectWithLabel: 'HTTP req/s'. > ZnLogEvent announcer > when: ZnServerTransactionEvent > do: [ :each | transactionCount := transactionCount + 1 ] > for: #transactionCountDemo. > [ [ > 1 second asDelay wait. > transactionsPerSecond value: transactionCount. > transactionCount := 0 ] repeat ] > forkAt: Processor userBackgroundPriority > named: #transactionCountDemo. > > Then we start the server: > > ZnServer startDefaultOn: 8080. > > In a terminal, we use ab (the Apache Benchmark tool) to generate some load on > the server (10K requests for 1K random data, using 4 concurrent threads): > > $ ab -k -n 10240 -c 4 http://localhost:8080/random/1024 > > Here is a short 2 minute screencast showing this little demo in action (be > sure to select the HD version): > > https://www.youtube.com/watch?v=gaUxPNq6_7c > > It starts by showing how a AnnouncementSpy can be used to monitor the server > starting up and handling a single request - the logging from the client is > visible as well. The lines in the AnnouncementSpy are not just text, but > full, detailed objects. We inspect and explore the same transaction from both > the client and server perspective. > > Next is the demo of the live updating requests per second monitor with the > load described above. You can see that both our counter and ab report > approximately the same number: about 800-900 req/s. > > And finally, here is the cleanup code: > > ZnLogEvent announcer unsubscribe: #transactionCountDemo. > ZnServer stopDefault. > Process allInstances select: [ :each | each name = #transactionCountDemo ] > thenDo: #terminate. > > Note that by using other data elements in the ZnServerTransactionEvent we > could track bytes transferring in or out, rates of failure, slow requests and > so. There are lots of possibilities with object logging left to explore, as > well as lots to learn. > > Sven > >
